Parking lock for the automatic transmission of motor vehicles

ABSTRACT

Parking lock which on the basis of an actuating signal triggered by the driver via an actuating device is engaged and disengaged by the fact that a piston ( 6 ) causes a detent disc ( 2 ) to rotate in such a way that, via a connection ( 19 ), a lock ( 17 ) is actuated which engages or disengages the parking lock. When engaged, the parking lock can be unlocked via a manual actuating device ( 13 ) causing an emergency release disc ( 3 ) to rotate by the fact that a bolt ( 4 ) likewise causes the detent disc ( 2 ) to rotate and then engages a detent unit ( 14 ) which maintains the parking lock in unlocked state. By repeated application of a hydraulic force to the actuating device ( 7 ) the detent unit ( 14 ) can be automatically disengaged by the detent disc ( 2 ) being caused to rotate.

The invention relates to a parking lock for automatic transmissions ofmotor vehicles where the output of the transmission is blocked by alocking pawl engaging in a parking interlock gear, the latter thus beingprotected against torsion.

BACKGROUND OF THE INVENTION

DE 43 17 257 describes a parking lock for automatic transmissions ofmotor vehicles where a locking pawl is drawn out from the parkinginterlock gear by a cylinder being filled with pressurized oil and thepiston thereof moving a connecting rod against spring tension via a gatemember. By manually moving a hand lever via an operative connection, theconnecting rod with the locking pawl can be moved in the gate member andthe parking lock is thus unlocked. By the piston rod having a directconnection with the connecting rod of the locking pawl and thus a linearmovement being directly transmitted to the connecting rod, via alinearly moved gate member, the operative connection, which also carriesout a linear movement since it ends in the passenger space of thevehicle, has to be expensively sealed in the automatic transmission.Should the parking lock be hydraulically unlocked, the locking pawl isdrawn out from the parking interlock gear by the connecting rod carryingout a linear motion which is drawn back by a pin passed in a diagonallyextending groove of the gate member. Thereby considerable frictionalforces appear between the pin and the diagonally extending groove. Ifthe parking lock is manually unlocked in an emergency and the pinengages in the gate member, this position can again be disengaged by thepiston of the hydraulic unit being loaded with pressure and the pinbeing enabled to leave the engagement. In this state, the possibilityexists that the pin impinges upon the forking of the grooves in the gatemember and being sheared off at the same time. By using a gate member,there is, likewise, the possibility that jerks during driving produce anundesired operation of the parking lock device, since a linearlysupported gate member constitutes a spring-mass system which reacts tolinear forces.

The invention is based on the problem of providing a parking lock for anautomatic transmission of a motor vehicle which stands out by greatoperational security, simple construction, reliable sealing and lowfriction.

SUMMARY OF THE INVENTION

The parking lock comprises a fixture which is connected with aconnecting rod having a locking pawl and is moved by a hydraulicactuating device comprised of one piston, one cylinder and one recoilspring. The fixture consists of two discs which are disposed on a commonshaft and by rotation of the discs operation of the parking lock can beactuated. The first disc, here called the detent disc, has a first,eccentrically mounted connection to a connecting rod having a lockingpawl, and, opposite to the first connection and eccentrically disposed,a second connection to a hydraulic actuating device. If the hydraulicactuating device is actuated, the parking lock is locked and unlockedexclusively by the rotary motion of the fixture. A second disc, herecalled the emergency release disc, has, via a pivot which can move in agroove in the detent disc, a connection to the detent disc, and aconnection via a central shaft, with which the emergency release disc isnon-rotatably connected, and upon which the detent disc is rotatablysupported, which shaft is connected outside the transmission via a sealin the housing of the transmission with an operative connection for theemergency release. The emergency release disc rotates within to stop andautomatically come to a position in which the parking lock is unlocked,via the emergency release, and thus the rotation of the emergencyrelease disc and, via the pivot, the rotation of the detent disc, and bya detent unit, preferably a spring, is kept in this position until thisposition is again turned back to the initial state by rotation of thefirst disc by automatic unlocking of the detent. By the fact that thediscs carry out a clear rotary motion, it is possible to easily supportthe central shaft of the discs in the housing of the automatictransmission and because the shaft is passed outwardly through thehousing of the automatic transmission, an operative connection can beeasily attached and the shaft sealed in the housing for reliableoperation. By not using any masses which have to be linearly moved, theinvention operates reliably even under great shock loads.

BRIEF DESCRIPTION OF THE DRAWINGS

From the descriptions that follow of the operations of the embodiments,other features essential to the invention can be inferred. A preferredembodiment of the invention is described herebelow with the appertainingdrawings which show:

FIG. 1 is a parking lock in which the parking interlock gear is blockedby the parking pawl;

FIG. 2 is a parking lock which is manually unlocked so that the parkingpawl releases the parking interlock gear;

FIG. 3 is a parking lock which is hydraulically unlocked so that theparking pawl releases the parking interlock gear; and

FIG. 4 is a parking lock of the above described type in sectionalrepresentation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1:

Within a housing 11 of an automatic transmission is located a parkinglock which comprises one fixture 1, one actuating device 7, one manualactuating device 13 and one lock 17. If no system pressure is producedby the automatic transmission, the actuating device 7 is pressurelessand the piston 6 is moved, via the spring 9, toward its stop in thecylinder 8 or the stop of the recess 5 on the pivot 4. The piston 6 isconnected, via a connection 18, via a detent disc 2 and via a connection19 with the lock 17 which consists of one cone and one parking pawl 16,the same as a parking interlock gear (not shown). By moving piston 6 toits stop in the cylinder 8, the detent disc is rotated by the connection18 around its central axis 20 and moves the connection 19, assisted bythe tension of the spring 9, so that at the lock 17 the parking pawl 16engages with the parking interlock gear and blocks the parking interlockgear. The detent disc 2 has a recess 5 in which pivot 4 is located,which is secured to an emergency release disc 3. The emergency releasedisc 3 is pressed by the tension of the spring 12 against the stop 10 onthe transmission housing 11. The force of the manual actuating deviceand of the spring 12 is applied via the shaft 21 to the emergencyrelease disc 3. For a better understanding, in FIGS. 1, 2 and 3, themanual actuating device is connected via a cam with the emergencyrelease disc 3. Since the stop 10 of the emergency release disc 3 abutsagainst the housing 11, the detent disc 2 is rotated until the recess 5abuts against the pivot 4 or the piston 6 in the cylinder 8. The detentunit 14 consists of a prominence 22 and a detent spring, which thedisengaged state, is located on the prominence 22.

FIG. 2:

In FIG. 2 is described the state in which the parking lock is manuallyunlocked. This is necessary when the vehicle has to be towed. By themanual actuating device 13 being actuated, the emergency release disc 3rotates until the stop 23 abuts against the housing 11. At the sametime, the spring 12 compressed. The pivot 4, which is fastened on theemergency release disc 3, abuts against the recess 5 of the detent disc2 and causes the detent disc 2 to rotate until the connection 19 unlocksthe lock 17. After the emergency release disc 3, with its stop 23, hasreached the housing 11, the parking lock is unlocked and the detent unit14 engages the prominence 22 in the emergency release disc 3. In thisposition, the vehicle can be towed.

FIG. 3:

FIG. 3 shows a position of the parking lock which unlocks the parkinglock by applying a hydraulic force. To this end, a hydraulic pressure issupplied to the cylinder 8 of the actuating device 7. The pressure actsupon the piston 6 and moves the piston and the connection 18. Therebythe detent disc 2 is caused to rotate and the cam 15 lifts the detentunit 14 so that the emergency release disc 3, with the prominence 22,can slide under the detent unit 14 until the stop 10 abuts against thehousing 11. The emergency release disc 3 and the manual actuating device13 can thus be returned to their initial state by the tension of thespring 12. The connection 19 is simultaneously moved by the rotation ofthe detent disc 2 so that the lock 17 is unlocked against the springtension 9. Thereby the detent unit 14 of the emergency release device isautomatically reset by applying a hydraulic pressure in the actuatingdevice 7. The detent spring can also have, on its free end, a rollermaking possible that the detent unit is more easily disengaged from thecam 15.

FIG. 4:

FIG. 4 shows a section through the fixture which demonstrates, inparticular, the simple attachment of the manual actuating device 13 onthe emergency release disc 3 via the shaft 21. This structural make-upprovides a simple and operationally reliable seal of the release fixture1. The shaft 21, and thus the detent disc 2 and the emergency releasedisc 3, can rotate around the central axis 20 and are supported in thehousing 11. The emergency release disc 3 is preferably connected by apin connection with the shaft 21. The detent disc 2 is rotatablysupported on the shaft 21.

Reference numerals 1 fixture 13 manual actuating device 2 detent disc 14detent unit 3 emergency release disc 15 cam 4 pivot 16 parking pawl 5recess 17 lock 6 piston 18 connection 7 actuating device 19 connection 8cylinder 20 central axis 9 spring 21 shaft 10 stop 22 prominence 11housing 23 stop 12 spring

What is claimed is:
 1. A parking lock for an automatic transmission of amotor vehicle, comprising: an actuating signal, triggered by a drivervia a hydraulic actuating device (7), for one of blocking and releasingthe automatic transmission; a parking pawl (16) movable via a rotatablefixture (1); the fixture (1) comprising, in combination with thehydraulic actuating device (7),: a first disc (2); a second disc (3);and a detent unit (14); the hydraulic actuating device comprising: apiston (6); a cylinder (8); and one recoil spring (9); and the parkingpawl (16) being one of movable manually from a vehicle space, via anoperating connection, and hydraulically movable via the actuating device(7); wherein the parking pawl (16) is moved to one of: (a) a disengagedstate by a rotation in a first direction of the fixture (1) around acentral axis (20), by a first pressurized shifting of the hydraulicactuating device (7), and, at the same time, bringing the detent unit(14) to an open state; and (b) is moved to an engaged state by arotation in a second opposite direction of the fixture (1) around thecentral axis (20), by a second pressureless shifting of the hydraulicactuating device (7).
 2. The parking lock according to claim 1, whereinthe fixture (1) comprises the first and second discs (2,3) disposed uponthe common central axis (20); and the first and second discs (2, 3) areconnected via a bolt (4) located in a recess (5) in the first disc (2)which delimits a torsion path of the first and second discs relative toone another.
 3. The parking lock according to claim 1, wherein torsionpaths of the first and second discs (2, 3) of the fixture are delimitedby a first stop surface (10) and a second stop surface (23).
 4. Theparking lock according to claim 2, wherein torsion paths of the firstand second discs (2, 3) of the fixture are delimited by a first stopsurface (10) and a second stop surface (23).
 5. A parking lock for anautomatic transmission of a motor vehicle, comprising: an actuatingsignal, triggered by a driver via a hydraulic actuating device (7), forone of blocking and releasing the automatic transmission; a parking pawl(16) movable via a rotatable fixture (1); the fixture (1) comprising, incombination with the hydraulic actuating device (7),: a first disc (2);a second disc (3); and a detent unit (14); the parking pawl (16) beingone of movable manually from a vehicle space, via an operatingconnection, and hydraulically movable via the actuating device (7);wherein the parking pawl (16) is moved to one of: (a) a disengaged stateby a rotation in a first direction of the fixture (1) around a centralaxis (20), by a first pressurized shifting of the hydraulic actuatingdevice (7), and, at the same time, bringing the detent unit (14) to anopen state; and (b) is moved to an engaged state by a rotation in asecond opposite direction of the fixture (1) around the central axis(20), by a second pressureless shifting of the hydraulic actuatingdevice (7).
 6. The parking lock according to claim 1, wherein thefixture (1) comprises The first and second discs (2,3) disposed upon thecommon central axis (20); and the first and second discs (2, 3) areconnected via a bolt (4) located in a recess (5) in the first disc (2)which delimits a torsion path of the first and second discs relative toone another.
 7. The parking lock according to claim 5, wherein torsionpaths of the first and second discs (2, 3) of the fixture are delimitedby a first stop surface (10) and a second stop surface (23).